The present invention relates to nuclear magnetic resonance (NMR) imaging and, more particularly, to novel methods for providing rapidly-obtained NMR profile images of cardiac wall and/or valve motion.
At the present time, the most utilized method of cardiac imaging is ultrasound echocardiography which provides a reasonably fast and interactive means to access cardiac motion and provide a relatively thorough investigation of the heart, with relatively low risk to the patient. However, it is well known that ultrasound echocardiography is limited to viewing of the heart from positions (through "windows") between the patient's ribs, as the relatively dense rib bones substantially interfere with ultrasound propagation. Present medical clinical practice generally includes a M-mode examination as part of a complete cardiac study. In M-mode ultrasound echocardiography, a continuous plot of the time-varying position of tissue interfaces, observed along a one-dimensional axis, is provided by the motion of the cardiac portion (walls and/or valve) to be imaged, moving with respect to a stationary pencil-shaped beam of ultrasound energy. However, not all patients provide a suitable "window" for such an ultrasound examination, and some patients have a limited view of certain cardiac features, such as the mitral valve and the like. It is therefore highly desirable to provide for a M-mode imaging method utilizing a modality other than ultrasound, which provides all of the features thereof, to access wall and/or valve motion, without being limited to windows provided through anatomical portions of differing density in the patient to be imaged, and yet still allowing accurate beam positioning and suitable contrast to be obtained. A noninvasive NMR cardiac examination allows well known NMR imaging techniques to be utilized to provide excellent overall images of the heart and define image coordinates and angles with respect thereto; it is therefore desirable to provide a M-mode technique to interactively probe the heart and provide a relatively rapid cardiac profile for continuously recording the motion of various wall and/or valve portions of the heart.